Muffler



Jan. 1, 1935. T. s. SAI-FORD 1,986,448

Filed July 2, 1950 Patented Jan. 1, 1935 UNITED STATES PATENT OFFICE 1Claim.

This invention relates to a muffler for engines of the intermittentfluid expansion type and particularly for internal combustion engines.

An object of the invention is to produce a 5 greater silencing of theexhaust, and at the same time to lessen the back pressure and preferablyactually to create suction on the exhaust. To this end I have found thatby cutting off from the exhaust stream small parts of the gases thereof,subjecting them to an impact to destroy the identity of puffs therein,and recombining said parts in a different arrangement to form a newstream the exhaust can be effectively silenced and preferably with anactual decrease in the pressure in the exhaust manifold.

In the accompanying drawing I have shown in:

Figure l a plan view of a preferred embodiment of my invention,

Figure 2 a cross section taken on line 2-2 of Figure l.

Referring particularly to Figures l and 2, I have shown a muffler lowhich receives exhaust gases from a manifold 11 and discharges them thruthe exhaust pipe 12. The muffler l0 is in the preferred embodiment acentrifugal blower having within its casing a rotor with blades or vanesi3 which closely t the interior of the casing except where it leads tothe outlet 14. In Figure 2 I have shown only one vane within the scopeof the inlet opening. It will be understood, how ever, that there may bemore. The number of the vanes is not material except to determine theproper speed relative to the motor at which the blower should be driven.I prefer to use four to six vanes and to connect the rotor to the motorso that one vane thereof will move from one edge of the inlet opening tothe other each time a cylinder I have found that this speed isparticularly advantageous since it allows each space between vanes toreceive from the exhaust the same cycle of pressures, that is the sainepart of the wave produced by the opening of an exhaust valve.

The shaft l5 of the blow-er rotor is shown hollow and mounted behind thefan so that it will be cooled by the current of air passing therethru.The shaft bearings are advantageously separated from the body of thecasing so as not to receive the full heat transmitted by the casing fromthe hot exhaust gases.

In the embodiment illustrated I have shown the blower driven from thefan belt. It will be understood however that it may be driven in anyother suitable way as by gearing or silent chain from the crank shaft,timing shaft or generator shaft, etc. The drive should however be suchas will drive the blower at the proper speed relative to that of themotor.

I have found the speed as described above, i. e. such that each vanemoves across the inlet opening in the period between exhaust impulses,to be a particularly advantageous one. Operating in this manner thespace between each two vanes receives an amount of gas equivalent to theexhaust from one cylinder and discharges it in a direction transverse toits original direction and parallel to the wave front from the originalstream. Thus the original stream which was composed of surges of gas athigh pressure grading off to lower pressures to be followed by anothersurge, is converted into a stream which is substantially uniform alongits length, and which if it varies at all to any important degree variesonly about its axis. It may thus be discharged to the atmosphere withoutcausing the propagation of sound waves corresponding to the opening ofthe exhaust valves. t the same time the blower, by its centrifugal andimpelling action, has decreased the pressure in the exhaust manifold,and thereby made for a more complete exhausting of the burnt gases fromthe cylinders and a correspending increase in the efficiency of themotor.

From what has already been said it will be obvious that the inlet to theblower should be away from the outlet 14, and should have an angularseparation therefrom in the direction of rotation of the rotor at leastas great as the angular separation of the vanes on the rotor. In otherwords, it should be impossible at any position of the rotor for gases topass directly from the inlet to the outlet. It is of course possible toposition the inlet closer and still to obtain some of the advantage ofmy invention, but it is not desirable, and insofar as that is done, thefunction of the blower is impaired.

Altho I have found it most advantageous to drive the blower so that eachvane travels completely across the inlet opening in the period be tweenopening of successive exhaust valves, nevertheless the muffler of myinvention may be operated quite satisfactorily at a slower speed suchthat more than the period between opening of valves is required for thevane to completely cross the inlet.

Altho I have shown and described above several, specific embodiments ofmy invention, it is to be understood that these are given by way ofexample only, and that my invention may be embodied in many other formsall of which are to be included within the scope of this application.

What I claim is:

A muiiier comprising a blower having a rotor with a plurality ofapproximately radial vanes, and an approximately circular casing ttingclosely over said rotor so as substantially to oonfine gases between theblades thereof, and having a tangential outlet and an inlet near itscenter but to one side thereof and angularly spaced from the outlet sothat it is always separated from the outlet by at least one of the vanesof the rotor, and means for rotating the impeller at a speed such thatthe blades thereof cross the inlet at intervals substantially timed tothose of the puis so that the charges cut 01T by successive impellersWill have substantially the same average pressures.

TRUMAN S. SAFFORD.

